Stent graft assembly and method

ABSTRACT

A method for assembling a stent graft onto a balloon delivery catheter is disclosed. The method includes the steps of: assembling a graft over a stent with attached security rings and inserting the ends of the graft between the stent and the rings; placing the assembled stent graft on the delivery balloon of the delivery catheter; and crimping the stent graft onto the balloon. The stent may include a plurality of axially aligned belts that include a plurality of mid belts, and first and second end belts, where each of the mid belts includes a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements, and each of the first and second end belts includes at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements. Also disclosed is a stent graft for use in practicing the method.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/028,742, filed Feb. 8, 2008 now U.S. Pat. No. 8,211,160, which is acontinuation of U.S. application Ser. No. 10/255,199, filed Sep. 26,2002 (abandoned), which is a continuation-in-part of U.S. applicationSer. No. 09/560,427, filed Apr. 28, 2000 and issued as U.S. Pat. No.6,520,984 on Feb. 18, 2003 (abandoned), each of which is incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to a stent graft assembly and method, andmore particularly to a stent graft assembly which includes securityrings.

BACKGROUND OF THE INVENTION

A composite expandable device with polymeric covering and bioactivecoating thereon, delivery apparatus and method are disclosed in U.S.Pat. No. 6,371,980, issued Apr. 16, 2002. In connection with theexpandable stent and the polymeric covering forming a graft carriedthereby it has been found that it may be possible for the graft to moveor become dislodged from its most desirable position on the stent. Thereis therefore a need for a new and improved stent graft assembly andmethod which overcomes this possible difficulty.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a stent graft that includes astent and a graft in the form of a polymeric sleeve extending over atleast a portion of the stent. Security rings are attached on oppositeends of the stent graft to prevent inadvertent displacement of the graftwith respect to the stent during deployment of the stent graft into avessel in a patient. In another embodiment, the security rings canreadily accommodate expansion of the stent graft. One or both of thesecurity rings may be attached to the stent with a weld. Preferably, theweld is a laser weld.

In one embodiment, the stent includes a plurality of axially alignedbelts which include a plurality of mid belts, and first and second endbelts. Each of the mid belts includes a plurality of circumferentiallyspaced struts having first and second ends adjoining firstsinusoidal-shaped elements. Each of said first and second end beltsincludes at least about twice the number of circumferentially spacedstruts adjoining second sinusoidal-shaped elements compared to thenumber of the struts in the mid belts.

In another embodiment, the first and second sinusoidal-shaped elementshave hinge points, and the second sinusoidal-shaped elements havenarrower hinge points relative to the hinge points of the firstsinusoidal-shaped elements.

The graft may be formed of ePTFE. In one embodiment of the invention,the graft includes a bioactive coating that is disposed on the graft.

One or more of the security rings of the invention may include aradiopaque marker carried thereon. In one embodiment, one or both of thesecurity rings includes an eyelet and the radiopaque material isdisposed in the eyelet.

Another aspect of the invention includes a method for assembling a stentgraft onto a balloon delivery catheter. The method includes the stepsof: assembling a graft over a stent with attached security rings andinserting the ends of the graft between the stent and the rings; placingthe assembled stent graft on the delivery balloon of the deliverycatheter; and crimping the stent graft onto the balloon. One or both ofthe security rings may be attached to the stent with a weld. Preferably,the weld is a laser weld.

In one embodiment of the method of the invention, the stent includes aplurality of axially aligned belts which include a plurality of midbelts, and first and second end belts. Each of the mid belts includes aplurality of circumferentially spaced struts having first and secondends adjoining first sinusoidal-shaped elements. Each of said first andsecond end belts includes at least about twice the number ofcircumferentially spaced struts adjoining second sinusoidal-shapedelements compared to the number of the struts in the mid belts.

In another embodiment, the first and second sinusoidal-shaped elementshave hinge points, and the second sinusoidal-shaped elements havenarrower hinge points relative to the hinge points of the firstsinusoidal-shaped elements.

The graft may be formed of ePTFE. In one embodiment of the invention,the graft includes a bioactive coating that is disposed on the graft.

One or more of the security rings of the invention may includes aradiopaque marker carried thereon. In one embodiment, one or both of thesecurity rings includes an eyelet and the radiopaque material isdisposed in the eyelet.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a stent graft assemblyincorporating the present invention mounted on the distal extremity of aballoon delivery catheter;

FIG. 2 is a side elevational view of another embodiment of a stent graftassembly incorporating the present invention also mounted on the distalextremity of a balloon delivery catheter;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2;

FIG. 4. is a view similar to FIG. 3 showing an alternate embodiment;

FIG. 5 is a side elevational view of a stent graft assembly with acertain portion of the stent graft being removed and showing the use ofdifferent types of security rings;

FIG. 6 is an enlarged view of one of the security rings shown in FIG. 5;

FIG. 7 is a view of a balloon with the stent graft with security ringsmounted thereon according to one embodiment of the invention;

FIG. 8 is a detailed view of the stent graft with security rings;

FIG. 9 is a plan view of a stent which has been split apartlongitudinally and spread out to show its construction; and

FIG. 10 is an enlarged view of a portion of the stent shown in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

In general, the stent graft assembly incorporating the present inventionis for use in placing a stent graft in a vessel of a patient andcomprises a balloon delivery catheter having a distal extremity andhaving an inflatable balloon on the distal extremity. A stent graft isdisposed over the inflatable balloon and is comprised of a stent and anouter polymeric sleeve, the sleeve having first and second ends. Firstand second expandable security rings are disposed over the first andsecond ends of the graft and serve to secure the first and second endsof the graft to the stent to prevent inadvertent displacement of thesleeve with respect to the stent during deployment of the stent graftinto the vessel of the patient.

More particularly as shown in FIG. 1 of the drawings, the stent graftassembly 10 includes a stent graft 11 which consists of a stent 12 whichis covered by a polymeric sleeve 13. As shown in FIG. 1, the stent graft11 is disposed over an inflatable balloon 16 on the distal extremity ofa balloon delivery catheter 17 of a conventional type and forming a partof the assembly 10. The balloon delivery catheter 17 includes amulti-lumen shaft 18 which incorporates a balloon inflation lumen (notshown) and may incorporate a guide wire lumen (not shown).

The balloon delivery catheter 17 and the stent graft 11 consisting ofstent 12 and the polymeric sleeve 13 are disclosed in U.S. Pat. No.6,371,980, issued. Apr. 16, 2002, which is incorporated by referenceherein in its entirety, and therefore will not be described in detail.As disclosed therein, the stent 12 is in the form of an expandable frameand consists of a plurality of axially spaced-apart circular belts 21which are interconnected by sinusoidal interconnector 22. Each belt 21is comprised of a plurality of circumferentially spaced-apart elongatestruts 24. Sinusoidal-shaped elements 26 and 27 adjoin the ends of thestruts 24 and form in conjunction therewith the circular belts 21. Thesinusoidal-shaped interconnectors 22 provided for interconnecting thebelts 21 are at circumferentially spaced-apart positions to provide astent 12 which when expanded is capable of providing circumferentialsupport while at the same time being axially flexible.

The stent 12 is typically formed of a suitable metal such as stainlesssteel, titanium and other metals and alloys thereof. It is desirablethat the material utilized for the frame be biocompatible with thefluids and tissue of the human body.

The sleeve 13 is in the form of a tubular member of a size so that itcan slip over the stent 12 when it is in an unexpanded condition andpreferably has a length so that the extreme ends of the stent 12 extendbeyond the sleeve as shown in FIG. 1. The sleeve 13 is typically formedof a polymeric material such as ePTFE.

In order to ensure that the polymeric sleeve 13 remains in the desiredposition on the stent 12, security rings 36 and 37 have been positionedover the outer ends of the sleeve 13. The security rings 36 and 37typically can be formed of a metal and preferably the same metal whichis used for the stent 12, for example, stainless steel or titanium oralloys thereof. The rings 36 and 37 have sinusoidal-shaped convolutions38 so that they can be expanded with the stent graft when the stentgraft is expanded as hereinafter described. By way of example, thesecurity rings can be formed from laser cut tubing in the same manner asstents having a suitable wall thickness of 0.003″ to 0.006″. The innersurfaces of the security rings can be left unpolished so that they havea rougher inner surface finish to enhance gripping to the outer surfaceof the sleeve 13. Alternatively, a texture can be applied to the innersurface to enhance the gripping capabilities of the security ring.

A radiopaque marker 41 is carried by at least one and, if desired, bothof the security rings 36 and 37, as in FIGS. 1 and 2. Thus, as shown, aradiopaque marker 41 is provided on the security ring 37 and can be of asuitable radiopaque material such as gold which has been cold worked orforged into an eyelet receptacle 42 formed as a part of the convolutions38. Alternatively, as shown in FIGS. 8 and 9, the radiopaque marker 148is provided on either or both ends of the stent 140 in a similar eyeletreceptacle 150.

In use of the stent graft assembly 10 and the stent graft 11 of thepresent invention with the method of the present invention, the stent 12can be placed upon a support mandrel (not shown) after which the sleeve13 is slipped onto the stent to provide the stent graft 11. The stentgraft 11 is then placed on the balloon 16 of the balloon deliverycatheter 17. The stent graft 11 is then crimped onto the balloon 16 witha crimping tool (not shown). The security rings 36 and 37 are thenplaced over the sleeve 13 and crimped onto the ends of the sleeve 13 bya crimping tool to ensure that the security rings 36 and 37 remain inplace on the ends of the sleeve 13 and also to ensure that the ends ofthe graft 11 frictionally engage the stent 12 to retain the sleeve 13 inthe desired position on the stent 12. Alternatively, the security rings36 and 37 and the stent graft 11 can be crimped simultaneously.

The stent graft assembly 10 shown in FIG. 1 can now be utilized forpositioning the stent graft 11 in a vessel of a patient in aconventional manner as for example by introducing the same through afemoral artery. The advancement of the stent graft 11 can be ascertainedby observing the positioning of the radiopaque marker 41 and also by anyradiopaque markers on the stent 12 and the balloon catheter 17. Duringadvancement of the stent graft to the desired site, the security rings36 and 37 serve to ensure that the sleeve 13 will not accidentallybecome dislodged or shifted in position on the stent 12. After the stentgraft has been delivered to the desired position in the vessel of thepatient, the balloon 16 of the balloon delivery catheter 17 can beexpanded to expand the stent 12 and the sleeve 13 carried thereby aswell as the security rings 36 and 37.

After the stent graft 11 has been delivered and then expanded thedesired amount, the balloon 16 of the balloon delivery catheter 17 canbe deflated and the balloon delivery catheter 17 removed in aconventional manner. The stent graft 11 will remain in place. Itsposition can be ascertained by observing the position of the radiopaquemarker 41.

Another embodiment of a stent graft assembly incorporating the presentinvention is shown in the stent graft assembly 61 in FIG. 2. The balloondelivery catheter 62 shown therein shows the use of radiopaque markerbands 63 and 64 positioned on a shaft 66 on opposite ends of the balloon67 and held in place by suitable means such as an epoxy 68 and disposedon opposite ends of the stent graft 11 and serve as enlargements toprevent the inadvertent dislodgement of the stent and/or the graft fromthe balloon during deployment of the stent graft 11.

In addition, as in the previous embodiments, security rings 71 and 72are provided on opposite ends of the stent 12 and the sleeve 13.Security rings 71 and 72 are each comprised of two elongate elements 76and 77 in the forms of waves or convolutions which are sinusoidal inshape and which are joined together by circumferentially spaced-apartaxially extending struts 78 and eyelets 79. As with the security rings36 and 37, it can be seen that the security rings 71 and 72 can bereadily crimped into place and expanded in the same manner as thesecurity rings 36 and 37. The eyelets 79 carry radiopaque markers 81. Aswith the security rings 36 and 37 the inner surfaces of the elements 76and 77 can be left unpolished or with a textured surface forfrictionally engaging the outer surface of the polymeric sleeve 13.

In order to further enhance the engagement between the polymeric sleeve13 on the stent 12, the radiopaque marker 81 as shown in FIG. 3 canprotrude out of the eyelet 79 so that it can form an indentation 82 withthe sleeve 13 which extends into an open. space in the stent 12 tofurther ensure a good engagement between the sleeve 13 and the stent 12to prevent dislodgement of the sleeve 13 and ring 71 or 72 from thestent 12. In a similar manner as shown in FIG. 4, an eyelet 86 providedon the stent 12 may also carry a radiopaque marker 87 protrudingradially and forming an indentation 88 in the inner surface of thesleeve 13 and to extend into a space in the security ring 72 to furtherensure good engagement between the sleeve 13 and the stent 12.

Operation and use of the stent graft assembly 61 shown in FIG. 2 is verysimilar to that hereinbefore described with respect to FIG. 1 with theprincipal difference being that the security rings 71 and 72 haveenhanced friction engaging capabilities over the security rings 36 and37 shown in FIG. 1. In addition, the balloon delivery catheter 62, byproviding the marker bands 63 and 64 on opposite extremities of thestent graft 11 also ensure that the stent graft 11 cannot accidentallybecome dislodged during deployment of the stent graft 11.

Still another embodiment of a stent graft assembly incorporating thepresent invention is shown in FIG. 5 in which the balloon deliverycatheter 62 as shown therein is similar to the one hereinbeforedescribed. The stent graft 11 is also similar to those hereinbeforedescribed. However, in FIG. 5 there is shown the use of security rings91 or 92 (showing two different designs) mounted on opposite ends of thesleeve 13. The security ring 91 is in the form of a stretchable polymerwhich can be stretched and fitted over one end of the sleeve 13 tofrictionally retain the security ring 91 on the sleeve 13 and similarlyto retain the sleeve 13 on the stent 12. Alternatively, as shown withthe security ring 92, a less stretchable band of polymeric material canbe utilized which is provided with circumferentially spaced-apartcutouts 93 therein which as shown in detail in FIG. 6 are positioned insuch a manner so as to provide weakened regions 94 associated with eachof the cutouts 93 but being staggered or provided on opposite sides ofthe security ring 92 so that when the stent graft 11 is expanded, theseweakened regions will or can break apart to provide a zig-zag shape or asubstantially sinusoidal wave-like shape, for the expanded security ring92. Thus, it can be seen that a polymeric security ring can be providedwhich firmly secures the graft to the stent while still permittingexpansion of the stent and graft after the stent graft assembly 11 hasbeen deployed to the desired position.

As shown in FIG. 7, the stent graft 100 is shown mounted on a deliveryapparatus 102. The apparatus 102 is provided with a central lumen 103which is adapted to receive a conventional guide wire. The lumen 103extends through the apparatus 102 and an opening (not shown) is providedin the apparatus for expanding the apparatus. The apparatus 102 has asubstantially continuous diameter and is provided with distal andproximal portions 104 and 106 and an intermediate portion 107 whichserves as a working portion of the apparatus, having a length which willaccept the length of the stent graft 100. Radiopaque marker bands 110and 111 are provided on the portion of the central lumen 103 extendingthrough the apparatus and are mounted in the distal and proximalportions 104 and 106 as shown adjacent to the intermediate portion 102.

As illustrated in FIG. 10, the stent 160 includes a plurality ofserially-connected belts 162 which are axially aligned with each otherand are interconnected by sinusoidal interconnector 164. Each belt 162includes a plurality of circumferentially spaced-apart elongate struts166. Sinusoidal-shaped elements 168 and 169 adjoin the ends of thestruts 166 and form in conjunction therewith the circular belts 162. Thesinusoidal-shaped interconnectors 164 provided for interconnecting thebelts 162 are at circumferentially spaced-apart positions to provide astent 160. Stent 160 is capable of providing circumferential supportwhile, at the same time, being axially flexible. The stent may be formedby forming the desired pattern directly out of a tube, e.g. by lasercutting or chemical etching. Alternatively, the desired pattern may beformed out of a flat sheet; e.g. by laser cutting or chemical etching,and then rolling that flat sheet into a tube and joining the edges, e.g.by welding. Any other suitable manufacturing method known in the art maybe employed for manufacturing a stent in accordance with the invention.Furthermore, stents may be formed by etching a pattern into a materialor mold and depositing stent material in the pattern, such as bychemical vapor deposition or the like. Such stents may be formed ofplastic, metal or other materials and may exhibit a multitude ofconfigurations. The metals from which such stents are formed may includestainless steels, titanium, Nitinol, and tantalum among others.

In one embodiment, stent 160 includes serially-connected belts 162, andtwo end belts 170 and 172. All belts are connected with serpentineinterconnectors 164. Each end belt 170 and 172 includes a plurality ofcircumferentially spaced-apart elongate struts 176. Belts 162 alsoinclude spaced-apart elongate struts 166. Serpentine interconnectingelements 164 are provided for interconnecting the plurality of belts 162and the end belts 170 and 172 so that the belts 162 and end belts 170and 172 extend along an axis while permitting axial bending between thebelts 162 and the end belts 170 and 172. Thus, with the constructionshown in FIG. 10 there are provided five belts 162 and two end portions170 and 172 with six sets of interconnecting elements 164. The number ofbelts and interconnecting elements may vary depending on the desiredlength of the stent graft.

As described above, a polymer sleeve 142 extends over substantially theentire length of the stent 160. With reference to FIG. 10, there aretwice as many struts 176 in end belts 170 and 172 as there are struts166 in belts 162. The larger number of struts 176 in end belts 170 and172 provides more circumferential support for the ends of the polymersleeve (not shown), without causing unduly high radial strength at theends of the stent graft. This has the advantage of preventing prolapseof the sleeve into the lumen of the stent graft due to blood flow afterthe stent graft is implanted into the vessel.

In addition, security rings 144 and 146 are provided on opposite ends ofthe stent 160 and the sleeve 142. The security rings 144 and 146typically can be formed of a metal and preferably the same metal whichis used for the stent 160, as for example stainless steel or titanium oralloys thereof. The security rings 144 and 146 have sinusoidal-shapedconvolutions so that they can be expanded with the stent graft when thestent graft is expanded. A radiopaque marker 148 may be carried by atleast one, and if desired both, of the security rings 144 and 146.Alternatively, as shown in FIG. 9, a radiopaque marker 148 is providedon both ends of the stent 160 and is of a suitable radiopaque materialwhich has been cold worked, forged into or deposited on an eyeletreceptacle 150 formed as a part of the convolutions. Examples ofmaterials which can be employed as radiopaque materials include, but arenot limited to, iodine and its salts or compounds, barium and its saltsor compounds, tungsten, rhenium, osmium, noble metals, palladium, gold,colloidal gold, silver, platinum, tantalum, iridium or their alloys.Preferably, the radiopaque material is gold, platinum, iridium,titanium, tantalum, or alloys. Such materials are highly visible byfluoroscopy even at very minimal thicknesses.

The security rings 144 and 146 may be attached to the stent 140 by anysuitable attachment mechanism to ensure that the security rings 144 and146 remain in place on the ends of the stent graft. This includes, butis not limited, to, suture attachment methods, e.g. where a suture goingaround one or more struts of the stent is attached to a security ring.Apart from suturing techniques, methods including adhesives also may beused. One can solder or braze the stent and security ring together.Preferably, the security rings 144 and 146 are welded to stent 140 atone or more weld points 152, 153, 154. One advantage of welding thesecurity rings to the stent is to improve the mechanical integrity ofthe stent graft system. The welding connections may be created bywelding techniques using welding technologies such as tungsten inert gas(tig) welds, metal inert gas (mig) welds, laser welds, friction welds,and electron beam welds. Other materials known to accelerate the weldingprocess and improve the strength between the welded elements can beadded. Electropolishing may be used to remove processing impurities andform a smooth surface following attachment of the stent to the securityrings.

In one embodiment, the stent graft is positioned in a vessel of apatient and the ends of the stent graft are opened first, and then themiddle of the stent graft is opened. This method maximizes the abilityof the stent graft to capture potential debris material from anunderlying stenosis in the vessel. With reference to FIGS. 10 and 11,the hinge points 201, 202, 203 and 204 of end belt 170 are narrower thanthe hinge points 210, 211, and 212 of belt 162. This feature providesthe advantage of requiring less force to open the end belts 170 and 172than belts 162.

The stent design and functionality in the embodiments described above isnot limited to a balloon-expandable stent, but may be employed with theso-called self-expanding stents that are formed for example from shapememory materials such as Nitinol.

From the foregoing it can be seen that there has been provided a stentgraft assembly and method which makes it possible to ensure that thegraft is maintained in the desired position on the stent at all timesand particularly during deployment of the stent graft while readilyaccommodating expansion of the stent graft after the stent graft hasbeen deployed into the desired position. It also can be seen that use ofthe security rings' serves to prevent inadvertent movement of the graftwith respect to the stent or separation of the graft from the stent.

What is claimed:
 1. A method of retaining a polymeric sleeve on a stent,where the polymeric sleeve is located over an outer wall of the stent,the stent including an opening, the improvement comprising: urging aportion of the polymeric sleeve from over the outer wall of the stentinto a volume of the opening, the volume of the opening being surroundedby an inner wall; and frictionally engaging the polymeric sleeve portionwith the stent between the inner wall and a member received within theopening.
 2. The method of claim 1, wherein the member comprises aradiopaque marker.
 3. The method of claim 2, wherein a plurality ofopenings are included in the stent, each opening receiving a radiopaquemarker engaging the polymeric sleeve.
 4. A stent graft for positioningwithin a body lumen, the graft comprising: a polymeric sleeve; a stentincluding an opening having a volume surrounded by an inner wall; and amember frictionally received within the opening such that the polymericsleeve is disposed within the volume of the opening and engaged betweenthe inner wall and the member.
 5. The stent graft of claim 4, whereinthe member comprises a radiopaque marker.
 6. The stent graft of claim 5,wherein a plurality of openings is included in the stent, each openingreceiving a radiopaque marker engaging the polymeric sleeve.
 7. Thestent graft of claim 4, wherein the opening is substantially circular.8. The stent graft of claim 7, wherein at least a portion of the memberis cylindrical.
 9. The stent graft of claim 4, wherein the memberextends through the opening when frictionally received within theopening.
 10. The stent graft of claim 9, wherein the member extendsradially through the opening.
 11. The stent graft of claim 4, whereinthe member is frictionally received within the opening without piercingthe polymeric sleeve.
 12. The method of claim 1, wherein thefrictionally engaging comprises inserting the member through the openingin a radial direction.
 13. The method of claim 1, wherein thefrictionally engaging comprises inserting the member into the openingwithout piercing the polymeric sleeve.
 14. The method of claim 1,wherein the urging comprises contacting the member against an outer sideof the sleeve.
 15. The stent graft of claim 4, wherein the membercontacts only an outer side of the sleeve, and an inner side of thesleeve contacts the inner wall.
 16. A stent graft for positioning withina body lumen, the graft comprising: a graft component; a stent includingan opening having a volume surrounded by an inner wall; and a memberfrictionally received within the opening such that a portion of thegraft component is disposed within the volume of the opening and engagedbetween the inner wall and the member.
 17. The stent graft of claim 16,wherein the graft component comprises a polymeric sleeve.
 18. The stentgraft of claim 16, wherein the graft component comprises a tubularmaterial extending over the stent.
 19. The stent graft of claim 16,wherein the member is frictionally received within the opening withoutpiercing the graft component.
 20. The stent graft of claim 16, whereinthe member extends radially through the opening.